Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
348 AM EDT Fri Sep 29 2023
Valid 12Z Fri Sep 29 2023 - 12Z Mon Oct 02 2023
...Sierra Nevada through the Northern Rockies...
A shortwave trough currently off the southern OR coast amplifies
as it digs south down the California coast through tonight before
closing into a low pressure system along the northern CA/NV border
Saturday night with little movement expected then through Sunday.
A plume of Pacific moisture streams into central/southern CA
tonight with precip spreading over the Sierra Nevada late tonight
and the Great Basin Saturday into Sunday. This anomalous low will
drive snow levels down to around 9000 ft during the heavier precip
Saturday through Sunday in the Sierra Nevada, the Great Basin
ranges, and the Northern Rockies. WPC probabilities for over 4" of
snow peak around 40% in the High Sierra on Day 2. This will likely
produce at least minor impacts at the highest passes including
Tioga Pass. As the precip spreads across the Great Basin to
northern Rockies Sunday, moderate snow is likely on the highest
ranges, though the Day 3 WPC probabilities for over 4" are
The probability of any ice accumulation across the CONUS is less
than 10 percent.